(1) Field of the Invention
The present invention relates to a transmission for a tractor having a transmission case supporting rear axles and directly coupled to an engine.
(2) Prior Art
A conventional transmission having a change speed gearing of a propelling system and a change speed gearing of a PTO system is disclosed in Japanese Utility Model Publication Kokai No. 63-26. In this known construction, transmission shafts forming part of the two change speed gearings, respectively, are juxtaposed vertically. Consequently, the transmission case has large vertical dimensions.
Where, as in the known construction, the transmission shafts forming part of the two change speed gearings are juxtaposed vertically, the transmission case has large vertical dimensions. Thus, in the case of a tractor with a transmission case acting also as a tractor frame, a step board placed on top of the transmission case has a center portion thereof bulging upward to a large extent. In this way the step board is clearly separated right and left, leaving narrow spaces for the driver's foot rests. When boarding or alighting from the tractor, the driver would find the bulging portion obstructive and could have his foot caught by that portion. In this sense, there is room for improvement from the point of view of comfort on the step board.
U.S. Pat. No. 4,824,128 discloses a transmission in which a change speed mechanism of a propelling system and a change speed mechanism of a PTO system are arranged at opposite sides of a longitudinal centerline of the transmission. This construction has a disadvantage that the transmission still has a considerably large sectional area.